mp_rendezvous & scheduling on particular cpus

I'm trying to gain some understanding of how mp_rendezvous works on x86, and I have a few questions:

• There are two variants, mp_rendezvous_no_intrs and mp_rendezvous. The first states that it disables interrupts during the execution of the requested function. However both boil down to mp_cpus_call1, which seems to disable interrupts for reasons not related to whether the "no_intrs" variant of mp_rendezvous was called (from osfmk/i386/mp.c), if the function is being called on cpus other than the master cpu:

	topo_lock = (cpus != cpu_to_cpumask(master_cpu));
	if (topo_lock) {
		ml_set_interrupts_enabled(FALSE);
		(void) mp_safe_spin_lock(&x86_topo_lock);
	}

Additionally interrupts seem to be disabled for the execution on the current CPU, as well:

	/* Call locally if mode not SYNC */
	if (mode != SYNC && call_self) {
		KERNEL_DEBUG_CONSTANT(
			TRACE_MP_CPUS_CALL_LOCAL,
			VM_KERNEL_UNSLIDE(action_func), VM_KERNEL_UNSLIDE_OR_PERM(arg0), VM_KERNEL_UNSLIDE_OR_PERM(arg1), 0, 0);
		if (action_func != NULL) {
			ml_set_interrupts_enabled(FALSE);
			action_func(arg0, arg1);
			ml_set_interrupts_enabled(intrs_enabled);
		}
	}

Finally, I noticed that if I have a function that is being called via mp_rendezvous, and trace it using DTrace, only the execution on the CPU that mp_rendezvous is called on hits the Dtrace probe. Is that because the other CPU's are executing the function on an interrupt thread when handling the IPI?

Thank you,

Neal